If you want to personalize the toolbar of your fck editor it is too easy. You only have to modify the web.config of your dnn aplication, and the fckconfig.js file of your fckeditor.

in the fckconfig.js file you can find the description of the toolbarset. if you are running the app from source, you can find it in [root]/Providers/HtmlEditorProviders/Fck/custom.

If you couldnt this file there, you can also see the path in the web.config of your dnn, in

<dotnetnuke>
        <htmlEditor defaultProvider="FckHtmlEditorProvider">
            <providers>

To know more about how you can personalize your fckeditor's toolbarset go to: http://wiki.fckeditor.net/Developer%27s_Guide/Configuration/Toolbar

dont forget to take a look in the webconfig, there you can see for example which toolbarset is using your dnn by default